"Being indifferent to reconnaissance in battle is analogous to a general hugging a rock and stepping into the abyss. With the employment of reconnaissance agents determine the day and time of battle. These two verses were written down from Shingen to Katsuyori" Ii House Military Methods
"When our forces are at a standoff with the enemy, report signs such as posts and stones indicating land boundaries in the separation area. Before preparations at the enemy’s camp take place, you have to identify his weak areas. For that, when sending scouting for land markers, have them return with observations of the conditions of the enemy’s encampment. However, if you overextend your activity, the enemy too will send scouts. As the enemy sends scouts, returning quickly would be disgraceful. Therefore, in such a situation, do your best to remain agile.
At the time of approaching the enemy’s camp for scouting, you should recognize that if there is a forest in that area and the birds are quiet, then there are no people in that area. However, if there are large trees, you should be more alert. Also, if in areas of the moat watchtower (hori yagura) the birds are not alarmed, then there are no people behind it. There you should climb up, observe, and return.
When you need to scout the enemy’s camp but you do not have a way [to do that], mix with merchants and proceed as one of them. Even if there is no camp at times of a stand off between us and the enemy, wine merchants will arrive [to sell wine]. If you naturally and smoothly approach as such a person, [their] guard will drop, [allowing you to] assess." Hosokawa Yūsai,
"Three levels of reconnaissance agents (monomi)
The three levels are Senior, Middle and Junior. The teacher said, the Senior observes while exposed and therefore there is no place left to be observed. The Junior observes while in concealment and therefore he observes only one segment. The Middle is in between the two and is not limited to either observing openly or observing while hiding. As such, the number of Middle [scouts] is in the middle [between Senior and Junior scouts]—less than Senior and more than Junior [scouts]. Observation is also mid-level. The Senior observes everything. The Junior observes a particular matter. The Middle observes by taking the middle road [between the two]. It is also said that, in general, the scout presses to observe, observes by inquiry, and observes the enemy in hiding, and there is nothing other than these three [methods]." Yamaga Sokō,
"...In the Japanese realm, it is called monomi. It is said that there are a few types: ō-monomi (senior scout), chū-monomi (middle-scout), shō-monomi (junior scout), tsunagi-monomi (linking scout), tomari-monomi (night-duty scout), aizu-monomi (signal-scout), tekazu no monomi (multiple-task scout), and soe-monomi (supporting scout), among others. In a certain record is stated that if a scout is vital for the assessing, contriving and manipulating of the army’s battle, brave and wise person must be selected. Long ago, during the turbulent world of the Genpei [War], when [Minamoto] Kurō Yoshitsune journeyed to the Western Provinces, Musashibō [Benkei] was a scout. Even if the old diaries disappear, [we know that] at that time, the nameless scouts were sent ahead to determine the enemy’s actions.” Kinoshita Yoshitoshi
"Make scouts an essential part of the army. At a crucial time in battle, [scout] are of primary importance. ...The major scouts of [Nitta] Yoshisada in the Suwa Battle, rather than doing things abruptly, they made an effort with difficulties and with extreme prudence. Now, the mission to inform matters to the base camp when scouting and regrouping, was completed. ... Hayashi Shihei